A turbocharger improves the efficiency of an internal combustion engine by harnessing the exhaust gas produced by the engine to power a turbine, which in turn rotates a compressor to deliver compressed air to the engine to increase the power and efficiency of the engine. Conventional turbochargers have turbines with fixed sizes and their performance characteristics are limited as a result. Large turbines are capable of producing large amounts of boost pressure, but are subject to longer “spool up” times as the volume of exhaust gas produced by the engine at low engine speeds is initially insufficient to turn the turbine wheel, requiring a steady buildup of exhaust gas pressure until the turbocharger can generate boost pressure. Turbochargers with small turbines are capable of generating boost pressure at low engine speeds using small volumes of exhaust gas, but deliver poor performance at high engine speeds because the smaller turbines cannot match the ability of large turbines to harness the large volumes of exhaust gas needed to drive the compressor to produce high boost pressure.
Variable geometry turbochargers represent a significant improvement over conventional turbochargers, and are equipped with movable vanes or other structures which modify the flow of exhaust gas into the turbine. For example, the vanes pivot at low engine speeds to force the exhaust gas through a narrow inlet, and the resulting high-velocity stream of gas turns the turbine wheel. When the engine operates at high engine speeds and the exhaust gas pressure rises, the vanes pivot to increase the size of the inlet, allowing a larger volume of exhaust gas to enter the turbine to allow the turbocharger to produce more boost pressure. Variable geometry turbochargers are responsive at low engine speeds yet also capable of delivering high boost pressure at high engine speeds. The movement of the vanes is achieved using an actuator controlled by a hydraulic solenoid system or a similar equivalent, which will cause the vanes to open automatically in response to increasing exhaust gas pressure within the turbine, allowing the turbocharger to provide steadily increasing amounts of boost pressure as the vehicle accelerates. However, in certain situations, the opening of the vanes will instead cause an undesirable drop in boost pressure. For example, vehicles engaged in off-roading or towing operations require sustained boost pressure at low vehicular speeds, thus presenting an application for which the default characteristics of the turbocharger are poorly optimized. Such as user may therefore wish to restrict the maximum size of the inlet between the vanes to enable the turbocharger to deliver sustained boost pressure at low engine and vehicular speeds.
Although there are various electronic systems which allow users to exert direct control over the actuator, these require significant modification of the turbocharger and the electrical system of the vehicle itself. Furthermore, retrofitting hydraulic actuators for electronic control is often undesirable and impractical. A need therefore exists for a device which allows users to adjust the extent to which the vanes can open to prevent premature drops in boost pressure without requiring significant modification of the engine or the turbocharger itself.
In the present disclosure, where a document, act or item of knowledge is referred to or discussed, this reference or discussion is not an admission that the document, act or item of knowledge or any combination thereof was at the priority date, publicly available, known to the public, part of common general knowledge or otherwise constitutes prior art under the applicable statutory provisions; or is known to be relevant to an attempt to solve any problem with which the present disclosure is concerned.
While certain aspects of conventional technologies have been discussed to facilitate the present disclosure, no technical aspects are disclaimed and it is contemplated that the claims may encompass one or more of the conventional technical aspects discussed herein.